A discharge lamp such as a deuterium lamp is used for a standard light source of various measuring instruments or the like. Techniques related to such a discharge lamp are described in Patent Documents 1, 2, 3 and 4 Such a discharge lamp is provided with: a closed vessel having gas encapsulated therein; a cathode constituted of a filament located in the closed vessel; an anode located in the closed vessel; and an aperture member, which has a first opening positioned on a discharge path between the cathode and the anode.
Moreover, a small discharge lamp is also under development. Discharge lamps described in Patent Documents 5, 6 and 7 disclose relatively small discharge lamps.
Such a discharge lamp is provided with a controller for controlling the lighting thereof. A current-limiting resistor is installed in series with a discharge current circuit in a lighting power source of a discharge lamp in order to correct the negative characteristics of the lamp, although a loss at the resistor simply causes lowering of the efficiency of the power source, without contributing to emission of the lamp at all. When the efficiency of the power source is low, the power consumption increases and a large power source becomes necessary and, therefore, miniaturization of a device becomes difficult.
Therefore, a device can be miniaturized by reducing the current-limiting resistance during steady discharge so as to enhance the efficiency of the power source. It is required to increase the current-limiting resistance only at the time of lighting of a discharge lamp, since a change in the lamp impedance is large immediately after the lighting of a discharge lamp, in other words, during preliminary discharge.    Patent Document 1: Japanese Patent No. 3064359    Patent Document 2: Japanese Published Examined Patent Application No. S56-29359    Patent Document 3: Japanese Published Unexamined Patent Application No. H4-303597    Patent Document 4: U.S. Pat. No. 5,530,319    Patent Document 5: International Publication WO2006/022144    Patent Document 6: International Publication WO2006/087975    Patent Document 7: International Publication WO2006/087976